Tissue sampling devices have been used for some time including an outer needle for enclosing and guiding an inner needle which has, adjacent its outer end, a tissue retrieval means. In one type of biopsy device, when the inner needle is projected out of the outer needle, into the tissue to be sampled, the tissue expands into the recess. Projecting the outer needle over the tissue-filled recess shears the tissue so that a sample remains in the recess. Withdrawing the needles allows retrieval of the sample for biopsy testing. Other biopsy devices also use a hollow outer needle and an inner needle.
In some instances, the introduction of the needles is accomplished manually so that the needles are in the vicinity of the area to be examined. There the needles are mounted in what is called a "biopsy gun" which carries the needles and, when cocked and released, drives the needles in proper sequence into the tissue to receive the sample specimens. One example of a biopsy gun is found in a U.S. Pat. No. 4,699,154, to Radiplast AB, issued Oct. 13, 1987. The use of such a gun enables a single physician to accomplish the biopsy.
The present invention is directed to a biopsy needle assembly which can be mounted in a biopsy gun and which has what may be called a "preset" position, that is, a position in which the point of the inner needle is retracted to the extent that it is adjacent the point of the outer needle. The gun has a sequential release in that the inner needle is first driven forcefully into the tissue about 7/8 of an inch to receive the tissue sample. In the second release the outer needle is projected over the inner needle to shear and capture the specimens.
In order that a physician may successfully operate a biopsy gun, he must first of all cock the gun and, secondly, insert the hub ends of the inner and outer needles into the gun. To facilitate this insertion, the present biopsy needle assembly is constructed to have a pre-loading locator called a "pre-set" position. This enables a physician to set the two hubs of the inner and outer needles prior to initiating the procedure. He can then insert the needles in the area and in the proper direction for the test. Once the needles are placed, the physician can then readily install the hubs into the gun. This is especially important when the physician wants to make more than one biopsy sequentially.